I. Field of the Invention
The present invention relates in general to wireless communication systems, and in particular, to a communication employing free-space optical networks.
II. Description of the Related Art
One of the biggest challenges in telecommunication system deployment is to maximize the speed and bandwidth of data communication to the greatest number of destinations. Each communication technology has its own advantages and disadvantages. In some cases, a combination of communication technologies is necessary to provide communication services to a variety of users.
Wired communication systems have the reliability, but are costly to deploy, and in some geographic regions, impossible to deploy. Fiber-optic communication systems, which are a special higher-speed, variety of a wired communication system, are attractive, but again are very costly to deploy in some areas. Radio frequency communication, on the other hand, does not require as much physical structure for deployment as a wired communication system, but is less reliable due to interference and fading conditions in certain geographic areas. Free-space optical communication has recently been investigated as an alternative to wired and wireless communication technologies. However, a cost effective and reliable free-space optical communication system is not heretofore known.
It is desirable to provide a communication system, and components therefore, that is cost effective and flexible to deploy, and capable of providing high bandwidth/data rate communication to any type of destination.
Briefly, according to one aspect of the invention, a communication system is provided that includes a free-space optical network. The free-space optical network comprises at least two optical repeater devices coupled to each other and at least one gateway device coupled to one of the optical repeater devices. The optical repeater devices have at least two optical ports and each detects an incoming free-space optical signal at one optical port and retransmits an outgoing free-space optical signal the same or the other optical port. The gateway device comprises an optical interface unit that interfaces free-space optical signals of the free-space optical network with electrical signals.
According to another aspect of the invention, there are several versions of optical repeater devices. The type of optical repeater device chosen depends on where in the optical network it is positioned, and the functions required at that point in the network. A basic version of the optical repeater device comprises two optical repeater circuits coupled between the two ports. Each optical repeater circuit detects, amplifies and retransmits an optical signal. A more advanced version of the optical repeater device employs phase adjustment of a detected signal prior to retransmission. Still a further advanced version of an optical repeater device comprises optical interface units (as opposed to the more simple optical repeater circuits) and a packet switch to enable media access control (MAC) layer addressing of data packets.
In deployment of the communication system, a plurality of optical repeater devices are cascaded throughout an area to relay optical signals across distances where they will be accessed. An access device is positioned in the optical network where it is desired to distribute data from the optical network to other networks or devices, and collect data from other networks or devices to be transmitted on the optical network. The access device is essentially an enhanced version of the most advanced optical repeater device, whereby a packet switch in the access device is used to interface data between the optical network and other networks or devices that are coupled to access ports on the packet switch.
The communication system of the present invention is very cost effective and flexible. At any point in the optical network, a gateway device can be deployed to gain access to the optical network. Moreover, when it is desirable to branch off the optical network to several other networks (electrical, optical, radio frequency, etc.) or devices, an access device is deployed. The communication system can interface with any other network or device using suitable interfaces between a generic electrical signal format (to and from which the optical signals of the optical network are converted) and the physical media type of another network or device.
An optional feature of the more basic versions of the optical repeater device is the provision of a switch between the optical repeater circuits to loop back an electrical signal in the event a photo detector in one of the optical repeater circuits become inoperative. This prevents termination of the signal, and allows for re-routing through another path in the network so that the data can reach its destination(s).
Still another aspect of the invention is an optical lens system useful at an optical port of an optical repeater device. The optical lens system comprises an incoming lens assembly for receiving and focusing a plurality incoming optical beams and an outgoing lens assembly. The incoming lens assembly and the outgoing lens assembly are designed to cooperate with each other as between optical repeater devices that communicate with each other. The incoming lens assembly comprises a main object lens and one or more additional lenses and a photo detector to detect light focused by the incoming lens assembly and generate at least one electrical signal representative thereof. The outgoing lens assembly generates the multiple optical beams that are received by the incoming lens assembly on another optical repeater device. The outgoing lens assembly comprises a beam splitter to split an outgoing optical beam into a plurality of identical beams, a plurality of photo detectors each for detecting one of the plurality of identical beams and generating an electrical signal representative thereof, a plurality of amplifiers each associated with a photo detector in the outgoing lens assembly to amplify the electrical signal output by a photo detector, a plurality of driver circuits each associated with an amplifier to generate a drive signal for each amplified electrical signal, a plurality of light emitters each associated with an amplifier to generate an optical beam based on the drive signal, and a plurality of object lens each associated with a light emitter to focus an optical beam radiated thereby for free-space transmission.